The present invention generally relates to light fixtures for illuminating architectural spaces. The invention has particular application in light fixtures using fluorescent lamps, such as the T5 linear fluorescent lamp, as the light source.
Numerous light fixtures for architectural lighting applications are known. In conventional parking garages and lots, low wattage high intensity discharge (HID) light fixtures and lamps have been the norm. However, energy consumption, performance and fixture costs have identified a need for improved lighting fixtures and performance in this usage, to obtain the required lighting levels with fewer fixtures.
Another light fixture presently used in a typical parking lot and warehouse environment comprises a troffer with at least one fluorescent lamp and a translucent lens shielding the lamp. The troffer includes an elongated fixture support, a pair of sockets at opposite ends to secure and provide power to the fluorescent lamp. The elongated lamp is typically oriented horizontally with the roadway or lighted surface below. The light fixture is thus intended to distribute emitted light to a wide area. However, since the fluorescent lamps distribute light radially, the illuminance that strikes at the floor or ground directly below the fixture is significantly higher than at an area more laterally remote from the light fixture. The area directly below the light fixture is generally considered at or near nadir, while the area laterally remote from the light fixture is disposed at higher angles from nadir. That is, the amount of light striking a unit area (e.g., lux=lumen/m2) decreases proportionally to its distance from an area directly below the fixture. This can result in uneven lighting, and areas of significantly less lighting remote from the light fixture or at an area between adjacent light fixtures.
An important factor in the design of light fixtures for a particular application is the type of light source. The fluorescent lamp has long been the light source of choice among lighting designers in many commercial applications, particularly for indoor office lighting. For many years the most common fluorescent lamps for use in indoor lighting have been the linear T8 (1 inch diameter) and the T12 (1½ inch diameter). More recently, however, smaller diameter fluorescent lamps have become available, which provide a high lumen output from a comparatively small lamp envelope. An example is the linear T5 (⅝ inch diameter) lamp manufactured by Osram/Sylvania and others. The T5 has a number of advantages over the T8 and T12, including the design of light fixtures that provide a high lumen output with fewer lamps, which reduces lamp disposal requirements and has the potential for reducing overall costs and energy consumption. The smaller-diameter T5 lamps also permit the design of smaller light fixtures.
Nevertheless, there remains a need and opportunity to provide a durable light fixture for certain architectural lighting spaces that distributes a greater amount of light at areas more remote from the area directly below the fixture, with fewer or a minimum number of light fixtures, and with less energy consumption.